Conventionally, board joint members (referred to as “relay substrate” hereinafter) for connecting between circuit boards such as a module board on which electronic components (e.g. IC chip, chip part) are mounted include a multi-contact connector (composed of a part as the plug side and that as the socket side) and a pin connector (contact pins are fixed onto a resin substrate).
In recent years, with miniaturization and higher functionality of such as mobile devices, there has been a trend in an increase of the number of connecting terminals between module boards. Accordingly, an effort is under way to reduce the pitch between connecting terminals of a pin connector. However, the joint part of a pin connector is undesirably likely to break due to the difference of dimensional fluctuations between the members composing the joint part when temperature changes or due to a large force when being subjected to an extraneous impact force.
Meanwhile, with higher speed and frequency of such as a mobile information device, the demand is growing for EMC (electromagnetic compatibility) against malfunctions due to extraneous electromagnetic waves or interference with other devices due to radiated electromagnetic waves. As a result, mounting technologies of circuit board for reliable electromagnetic shielding are highly demanded. In a relay substrate connecting circuit boards on which a high-frequency component such as a control IC chip is mounted, extraneous electromagnetic waves and those radiated from the inside of the high-frequency component need to be electromagnetically shielded reliably.
To solve these problems, a relay substrate is disclosed that fixedly retains lead terminals in a given shape, made of thin metal plates with a spring elasticity, onto an insulative housing in a preliminarily set arrangement (refer to patent document 1 for example).
In the board joint member presented in patent document 1, a lead terminal is partially embedded in the housing, where one end is exposed on the bottom end surface of the housing to form a bottom-end joint part; the other end is exposed on the housing wall and rises to form a deformable part. The external wall surface of the housing is provided thereon with a shielding member.
The document describes that this structure allows connecting between circuit boards at a fine pitch and largely improving the impact resistance. Further, the electronic component is electromagnetically shielded from such as noise with a shielding member provided on the relay substrate.
Meanwhile, as shown in FIG. 11, the example is disclosed where one main surface of dual surface-mounting printed-circuit board 600 has circuit component 610 for the tuner section requiring electromagnetic shielding, mounted thereon, and the other main surface has circuit component 620 for the VIF (video intermediate frequency) section, mounted thereon, where circuit component 610 for the tuner section is electromagnetically shielded by metal case 630 (refer to patent document 2 for example). The document describes that this structure allows reliably shielding a circuit component requiring electromagnetic shielding along with downsizing, reduction in profile, and slimming down.
However, the relay substrate according to patent document 1 arranges and fixedly retains lead terminals with spring elasticity, preliminarily formed in a given shape, onto an insulative housing, and the external wall surface of the insulative housing has a shielding member formed thereon. Although this structure improves fine-pitch connection and impact resistance, slimming down the relay substrate is difficult and the production cost increases.
According to patent document 2, the metal case and the main surface of the printed-circuit board can electromagnetically shield the circuit component. However, as an additional component for electromagnetic shielding, the metal case by itself increases the total weight and volume, which goes against the current of the times toward device miniaturization. Additionally, to mount circuit components at a high density, the metal case needs to be subjected to such as insulation process before mounting the components, which decreases the productivity and increases the production cost.
Patent document 2 does not disclose a technique of connecting plural circuit boards with such as a relay substrate.    [Patent document 1] Japanese Patent Unexamined Publication No. 2005-333046    [Patent document 2] Japanese Patent Unexamined Publication No. H05-29784